Ophthalmic lens



July 21, 1936. E. TILLYER ET AL ,0

OPHTHALMIC LENS Filed Dec. 12. 1950 2 Shets-Sheet 1 INVENTOR 500 41? 0.TILLYEIP.

- HARPYW/l/LL July 21, 1936.

Filed Dec. 12. 1930 E. D. TILLYER ET AL OPHTHALMIC LENS INVENTOR EDGARD.TILLYER.

HARRY WHILL.

BY JZK 7 2 2321 2 Sheets-Sheet 2 Patented July 21:, 1936 orn'rnsmrc LENSEdgar D. Tillyerand Barry W. Hill, Southbridge, Mass., assignors toAmerican Optical Company, Southbridge, Mass, a voluntary association ofMassachusetts Application December 12, 1e30, Serial NJ. 501,867 3Claims. (01. 88-54) This invention relates to improvements in ophthalmiclenses and has particular reference to an improved bifocal or multifocallens and'process of making same. t

The principal object of the invention is to provide improved and lessexpensive means of producing lenses embodying fusion processes, bysubstituting molding processes'for certain of the more expensivegrinding and polishing operations hitherto employed without detractingfrom the excellence of the finished lenses.

Another object of the invention is the production of a fused multifocalor bifocal lens wherein the objectionable and harmful edge reflectionsof the fused segment are maintained at a minimum.

- Another object of the invention is, to provide improved means forproducing a fused bifocal or multifocal lens embodying the use ofmolding operations for forming the segment and the segment recess sothat either a feather or thin edge segment or a thick edge segment maybe used. I

Another object of the invention is to provide improved means for makinga molded segment button having reinforcement so located that the opticalproperties of the glass material is not destroyed in the molding,pressing or fusing operations.

Another object of the invention is to provide improved and lessexpensive means of producing a segmental button for a fused bifocal ormultifocal lens.

Another object of the invention is to'provide improved means. of makinga segment for a fused multifocal or bifocal lens of irregular orunsymmetrical shape or contour.

Other objects are the provision of means for controlling the size, shapeand optical center of the segments of such lenses, for controlling theposition of the dividing line of the segment, for controlling the amountand position of prism correction in the segment, for reducing the coststruction, arrangement of parts and the steps of the process withoutdeparting from the spirit of the invention as expressed in the accompanying claims. We, therefore, do not wish to be limited to the exactdetails of construction and 5 steps of the process shown and describedas the preferred forms only have been given by way of illustration. 1

Referring to the drawings:

Fig. I is a front elevation of a finished lens'l0 embodying theinvention.

Fig. II is a section on line 11-11 of Fig. I;

Fig. 111 is an enlarged sectional view of a semifinished lens blankshowing a step in the process of manufacture; 15

Fig. IV is a front elevation of the blank for the-reading additionshowing a step in the process of manufacture;

Fig. V is a front elevation of the segment for the reading additionillustrating a further step in the process of manufacture;

Fig. V1 is a sectional view taken on line VI-VI of Fi v:

Fig. VIII is an enlarged sectional view showing the segment illustratedin cross section in Fig. VI positioned within the countersink in themajor portion of the lens and illustrating in dotted lines how thefinished lens is formed from this major blank; I r

Fig. VIII is a front elevation similar to shown in Fig. IV, butillustrating a modified form of the invention;

Fig. IX is a sectional view taken on line lX-IX I of Fig. VIII; n

Fig. X is a view similar to Fig. VIII" showing another modified form ofthe invention;

Fig. m is a view similar to Fig. X showinganother modified form of theinvention;

Fig. 1a: is a view similar to Fig. XI showing a further modification ofthe invention;

Fig. m is a view similar to Fig. XII showing a still furthermodification of the invention;

Fig. XIV is a diagrammatic view illustrating how the position of thereading addition may be varied with respect to the center of thedistance portion or major portion of the lens;

Fig. XV is a front elevation of a lens showing the centers monaxiallyarranged and the dividlng line between the distance and reading fieldspositioned below the center of said fields;

Fig. XVI is a sectional view taken on line XVI-4W1 of Fig. XV;

Fig. XVII is a view similar to Fig. XV showing the center of thedistance field above the center of the reading field and showing the"dividing line between the two fields as lying on the center of saidreading field;

Fig. XVIII is a sectional view taken on line XVIIIXVIII of Fig. XVII;

Fig. XIX is a view similar to Fig. XV showing -the centers of thereading and the distance fields positioned one above the other andshowing the dividing line between the said reading and distance fieldslying between the centers of said fields;

Fig. xx is a sectional view taken on line XXXX of Fig. XX;

,Fig. XXII is a front elevation of a further "modification of the blankfor the reading addition;

Fig. XXIII is a section on line XXIIIXXIII of Fig. XXII;

Fig. XXIV is a front elevation of a further modification of the segmentfor the reading addition;

Fig. XXV is a section through the composite button;

Fig. IQIVI is a sectional view showing the composite button fused in thecountersink in the major portion of the lens; and

Fig. IQIVII is a view similar to Fig. XXVI showing the segment side ofthe lens finished with a continuous curve.

In the past fused bifocal or multifocal lenses have been made with verydesirable and emcient segments having a substantially straight upperedge and a. circular lower contour. These segments were made of twopieces of glass of different indices of refraction fused along the socalled straight edge of the segment but great dimculty was found in thefusing of this edge. The percentage of waste was exceedingly high andthe quality of the fused edge very poor. It is therefore one of theprime objects of this invention to provide means whereby this fusingdifiiculty is avoided.

There have also been produced in the prior art two types of fused lensesof this character one having the lower circular portion of the segmentof a knife or feathered edge and the other having the said edge of anappreciable thickness. Our invention may be employed with equal facilityfor either type of lens described.

Referring to the drawings wherein similar reference characters denotecorresponding parts throughout: In Figures I to VII inclusive we haveshown our invention as applied to the production of a segment for afused multifocal or bifocal lens having its lower circular outline ofthe thin or feathered edge type. In Figures VIII to XIII inclusive wehave shown it applied to a segment having said outline of an appreciablethickness. The other figures represent either one or the other of thesetypes. 1

In Fig. I we have shown a lens having the major portion 2 preferably ofcrown or other glass having a low index of refraction. In this majorportion 2 we grind and finish the countersink curve 3, see Fig. III.This curvature is finished to an optical surface and is of a radius suchas to produce the required power as in prior art lenses. We make thebutton portion in two pieces namely 6 of glass of the same index ofrefraction as the major portion 2, and 5 of a glass of a dlfierent indexof refraction; preferably of a high index of refraction such as flintglass or a barium glass. The top edge 6 of the portion 5 is shaped tothe desired line of the top edge of the segment. The lower edge of thepart A is shaped to fit around the shaped edge 6. These two pieces 4 and5 are then fused together. We then locate the desired position I of theoptical center of the segment and strike the circle 8 about the center Ito give the outline of the button. The blank is cut on the line 8 andthe countersink curve ll of the button, which is a curve on an axispassing through the center I is ground and finished to an opticalsurface which produces a button as shown in Figs. V and VI. This buttonis placed in the countersink 3, the surface II in contact with thesurface 3. The parts are then fused together as shown in Fig. VII. Thesegment side of the blank is finished to an optical power surface 9, andthe other side to an optical power surface Ill to produce the finishedlens shown in Fig. 11.

It will be noted that the line 6 may be shaped to practically anydesired contour and that this shape will be kept throughout all theoperations of production. An irregular contour line 6 of a shape that isdiflicult or even impossible to grind may be formed in this way, and along fusing surface for the line 6 may be provided. It will also benoted that the circular line 8 of the segment has a thin or featheredge. This feather edge is desirable in a finished lens as there areless reflections of light from such an edge than there are from a thickedge. This absence of reflections is a desirable consideration in thegreater number of finished lenses that are provided for the market'andis not departed from unless for some other special requirement notobtainable with the thin edge segment as will be pointed outhereinbelow.

In the structures shown in Figs. VIII to XIII inclusive a three partbutton is produced. The parts I! and I3 are of glass of sensibly thesame index of refraction as the major portion 2, and the segment id isof glass of a different index of refraction preferably of a high indexof refraction such as flint or barium glass.

The object of this construction is to enable the use of irregular or oddshaped segments difficult if not impossible to grind as well as asegment having an edge with an appreciable thickness all around. Theparts I2 and I3 are shaped to fit together on the line I6 as well as tofit around the edge E5 of the segment It. The position I? of the opticalcenter of the segment is determined and located and the circle 8 struckfrom the center H. The parts are fused together and cut on the line 8.The underside II is then surfaced as described above. This button isthen placed in the countersink as described above and fused therein. Inthis way many various shapes of segments may be obtained some of whichare shown in Figs. VIII and X to XIII inclusive.

It will be noted that the circle line 8 does not strike the segment linehence the segment in the button will have edges of an appreciablethickness. Segments with thick edges are of use where it is desired tointroduce a prism correction into the segment. Such segments toomaintain their size and shape during the surfacing of the segment faceof the lens until such edges have been ground through. Hence no outsidecontrol of the size and shape of the segment is needed other than not togrind entirely through the thickness of the segment. Where segments withthin edges are used an outside control by I r the operator is necessarybut is well understood and largely employed in the prior art.

A third method of making the button is shown in Figs. XXII to XXVIIinclusive. A piece 30 of glass of sensibly the same index of refractionas the major portion 2 has compressed or moulded therein while in aplastic condition from heat treatment the outline shape 3! of thesegment. 0n the bottom-of the piece 30 is left a web sec.- tion 32. Thisweb is left to provide a support or backing to the piece 30 when the diehaving the shape of the segment is pressed into the glass.

It provides a place for the displaced glass to flow and insures that theedge 33 is clean cut and smooth and that the glass adjacent the edge 33is homogeneous and without compression striae and without compressionstrata of different densities and that the lower edge of the compressedportion is clear cut and not deflected as it would be if there were noweb 32 to take care of the displaced. material. It has been found thatthe edge 33 when moulded or pressed as described above is clear andsmooth and that it provides a good fusion surface, in fact the fusionhas been found to be not only less expensive but superior to that offusing a fitted ground and polished edge as was done in the prior art.This compressing of the segment shape in the button as may be readilyseen isconsiderably cheaperthan the previous grinding'and polishingoperations. The segment 3 4 may be moulded to shape br it may be cut andfinished. The moulded segment is considerably less expensive and hasbeen found to give good results. The segment 3. is placed in the recess3! in the piece 30 and the parts fused together. The segment 34 is offlint or barium glass or a similar glass of high index of refraction.

After the parts 30 and 34 have been fused together the under surface 35which is the side opposite the web 32 is finished to the desiredcountersink curvature to produce the required power. The compositebutton is then placed in the countersink 3 with the surface 85 engagingthe countersink surface and the parts fused together as shown in Fig.XXVI. During the'fusing of the composite button into the countersink ofthe major blank the web 32 protects the segment 34 and prevents warpingetc. during the fusing operations.

The lens surfaces 9 and iii are finished as has been previouslydescribed with the other forms of buttons.

,The relationship of the optical centerof the segmenttothe center ofthe-major blank may bei'regulated as desired. In Figs. XV and-XVI theoptical center I or I! of the segment is located at the center of themajor blank. In Figs. XVII and XVIII the optical center I is below thecenter 36 of the major blank and on"the dividing line between thesegment and the major blank. In Figs. XIX and n the optical center I ofthe segment is below the center 36 of the major blank and also below thedividing line between the seer ment and major blank. This relationshipcan be arranged as desired as well understood inthe" prior art. Thecenters can also be placed .to either side of the vertical center lineof the lens as shown in Figs. X and XI. The dividing line too can beplaced as desired as well known in the considerations, the meltingtemperatures for fusion and the expansion for fusion.

The amount and position of prism correction is controlled by means ofthe angular relationship of the curve 8 to the segment as illustrated inFig. Xlfl. The position of the optical center with relation to thecenter of the major blank It will be understood that in all instancesthe portion'of the button which is of sensibly the same index ofrefraction asthe major portion will blend with the said major portionwhen fused thereto and disappear leaving only the portion of a differentindex of refraction visible.

The shapes set out in the drawings are simply by way of illustration ofhow various shaped segments can be obtained and how segments of varyingsizes may be obtained and are not intended to restrict applicant in anyway to the particular shape or size of segment shown.

As stated above the center of the reading addition may be 'placed in anydesired relation with respect to the center 36 of the major portion 2and the dividing line 6 may be located in any desired relation withrespect to the center 36 of the distance portion and the center I! ofthe reading addition.

It will be understood that wherever the term multi-focal is employed inthe specification or claims herein, that it refers to a bifocal lens aswell as other lenses having more than one focal field. It will also beunderstood that the use of the invention and device described hereinwill be mainly in connection with bifocal lenses, the greater bulk ofthe lenses to which this invention will be applied being bifocal lenses;only a small percentage will be trifocals or lenses of more than twofocal fields.

From the foregoing it.will be seen that there have been provided simple,emcient and economical means for obtaining all of the advantages of theinvention.

Having described our invention we claim:

'1. A blank for an ophthalmic lens comprising a major portion of glassof one index of refraction having acountersink therein and a compositebutton supported in said countersink, said composite button comprising aportion of glass of sensibly the same index of refraction as the majorportion and having a recess therein extending from the internalportion'of the glass but to a marginal edgethereof and having a webportion in said recess, and a segment of glass of a different index ofrefraction fitted in said recess between the web and major portion ofglass with one of its edges abutting the internal edge of the portionhaving the recess therein, a surface engaging the surface of the web inthe recess and a surface engaging the surface of the countersink andhaving the outline shape of the recess.

2. A blank for a fused ophthalmiclens comprising a major portion ofglass of one index of refraction having a spherical countersink recesstherein, a composite button fused in said countersink and a continuousoptical surface over said major portion and composite buttonintersecting the curve of the countersink, said composite buttoncomprising a portion of glass of sensibly the same index of refractionas the major portion and a portion of glass of a diiferent index ofrefraction fitted together edge to edge on a comating line of division,the piece of glass of sensibly the same index of refraction as the majorportion having a part along its edge forming the comating line ofdivision indented with respect to the re.- mainder of said edge, saidindentation having a central portion extending in a directiontransversely of the blank and angularly deflected opposed end portionswhich depart from the general shape of the central portion, and theother piece of glass of said composite button having a projectioncomplementary to said indentation, said complementary edges beingadapted to complete the outline of the top portion of the segment andthe remainder of the outline being formed by the intersection of thecountersink curve by said continuous optical surface over said majorportion and composite button.

3. A blank for a fused ophthalmic lens com prising a major portion ofglass of one index of refraction having a spherical countersink recesstherein; a composite button fused in said countersink and a continuousoptical surface over said major portion and composite buttonintersecting the curve of the countersink, said composite buttoncomprising a portion of glass of sensibly the same index of refractionas the major portion and a portion of glass of a difierent index ofrefraction fitted together edge to edge on.a comating line of division,the piece of glass of sensibly the same index of refraction as themajorportion having a part along its edge forming the comating line ofdivision indented with respect ,to the remainder of said edge, saidindentation having a central portion extending in a directiontransversely of the blank and terminating in opposed curved end portionswhich depart from the general shape of the central portion, and theother piece of glass of said composite button having a projectioncomplementary to said indentation, said complementary edges beingadapted to complete the outline of the top portion of the segment andthe remainder of the outline being formed by the intersection of thecountersink curve by said con-

